A typical centrifugal pump includes a motor driven shaft which penetrates the pump housing. The shaft is sealed to the housing by a mechanical seal assembly and is supported by either a hydrostatic or other suitable bearing means. During pump operation, the unbalanced radial load at the pump impeller, an inherent characteristic of centrifugal pumps, causes the shaft to shift and/or bend. The shaft may also be displaced in the vertical direction (axial) during operation due to shaft end thrust (pressure loading) and thermal expansion. The magnitude and rate of shaft displacement and/or bending are dependent upon system operating conditions, such as operating temperature, pressure, and pump flow rate. Maximum radial displacement or offset of the shaft occurs close to the position of the seal elements of the seal assembly and affects the performance thereof.
It is well understood that mechanical seal assemblies for use in nuclear and/or toxic fluid assemblies must meet higher standards of durability and "forgiveness" than mechanical seal assemblies used in less exotic applications. It is, therefore, desirable to test a seal assembly for a nuclear reactor pump under simulated conditions rather than in an actual application. In this manner, the manufacturer can readily determine whether the seal assembly is durable for its intended use.